Potassium permanganate oxalate titration

Quantitative Analysis. OxaUc acid is precipitated as calcium oxalate from a solution containing oxaUc acid, and the calcium oxalate obtained is then weighed. If there are no organic substances other than oxaUc acid present, oxaUc acid can be titrated quantitatively with potassium permanganate. 

An example of catalytic action is provided by the titration of oxalates with potassium permanganate solution referred to above. It is found that even though the oxalate solution is heated, the first few drops of permanganate solution are only slowly decolorised, but as more permanganate solution is added the decoloration becomes instantaneous. This is because the reaction between oxalate ions and permanganate ions is catalysed by the Mn2+ ions formed by the reduction of permanganate ions ... 

The excess of oxalic acid is titrated with standard potassium permanganate solution. 

Weigh out accurately 0.3-0.4 g potassium persulphate into a 500 mL conical flask, add 50 mL of 0.05 M-oxalic acid, followed by 0.2 g of silver sulphate dissolved in 20 mL of 10 per cent sulphuric acid. Heat the mixture in a water bath until no more carbon dioxide is evolved (15-20 minutes), dilute the solution to about 100 mL with water at about 40 °C, and titrate the excess of oxalic acid with standard 0.02 M potassium permanganate. 

The amount of oxalic acid thus decomposed under conditions where all the light is absorbed by the uranyl ion is determined by titrating a sample of the solution with potassium permanganate before and after irradiation. Since... 

Procedure Weigh accurately about 6.3 g of pure oxalic acid (AnalaR-Grade) into a 1 litre volumetric flask, dissolve in sufifcient DW and make up the volume upto the mark. Pipette out 25 ml of this solution, add to it 5 ml of concentrated sulphuric acid along the side of the flask, swirl the contents carefully and warm upto 70°C. Titrate this against the potassium permanganate solution from the burette till the pink colour persists for about 20 seconds. 

Procedure Weigh accurately about 1 g of sodium nitrite and dissolve it in DW to make 100 ml in a volumetric flask. Transfer 10 ml of this solution into a mixture of 50 ml of 0.1 N KMn04, 100 ml of water and add 5 ml of sulphuric acid along the side of the flask. Heat the contents to 40°C, allow it to stand for 5 minutes and add 25 ml of 0.1 N oxalic acid. Warm the resulting mixture to about 80°C on a steam-bath and titrate with 0.1 N KMn04 solution. Each ml of 0.1 N potassium permanganate is equivalent to 3.450 mg of NaN02. 

Elemental composition Ca 40.04%, C 12.00%, O 47.96%. CaCOs dissolves in water in the presence of a few drops of HCl. The solution is analyzed for calcium by AA or ICP spectroscopy or by treatment with ammonium oxalate followed by titration with potassium permanganate. 

Elemental composition Mn 63.19%, 0 36.81%. The pure oxide may be characterized by x-ray crystallography. The Mn02 content in pyrolusite may be measured by titration. An excess of a standard solution of oxalic acid is added to a solution of Mn02 in sulfuric acid. After all solid Mn02 dissolves, the excess oxalic acid is measured by titrating against a standard solution of potassium permanganate (see Reactions). 

Elemental composition Na 34.32%, C 17.92%, 0 47.76%. The aqueous solution is analyzed for sodium by AA or ICP method. The oxalate ion is quantitatively determined by titration against a standard solution of potassium permanganate. 

Selenious acid readily decomposes potassium permanganate, but analytical results are untrustworthy in the presence of more than a limited quantity of sulphuric acid.1 The oxidation should be carried out at 50° C., a known quantity of 0-lN potassium permanganate being used and the excess determined either by means of standard oxalic acid solution or by electrometric titration with ferrous sulphate. In the presence of tellurium, the latter is also oxidised and should be determined in a separate sample by oxidation with potassium di-chromate, which does not oxidise the selenium, and the necessary deduction can then be made.2... 

Tellurous acid cannot be determined by oxidation with potassium permanganate in acidified solution, but in alkaline solution accurate results may be obtained by cooling to 8°-10° C. after the oxidation and slowly acidifying with dilute sulphuric acid, with continual stirring. Excess of standard oxalic acid is then added and after warming to 50° C. the remaining excess is titrated with permanganate.6... 

Step 3 Heat the solution to 60°C and titrate the oxalate with standardized potassium permanganate until the purple end point of Reaction 7-1 is observed. 

Potassium permanganate can be standardized by titration of sodium oxalate (Na2C204) by Reaction 7-1 or pure electrolytic iron wire. Dissolve dry (105°C, 2 h) sodium oxalate (available in a 99.9-99.95% pure form) in 1 M H2S04 and treat it with 90-95% of the required KMn04 solution at room temperature. Then warm the solution to 55-60°C and complete the titration by slow addition of KMn04. Subtract a blank value to account for the quantity of titrant (usually one drop) needed to impart a pink color to the solution. 

Other kinds of titrations are possible in addition to acid-base titrations. For example, the concentration of a solution of potassium permanganate, KMn04, can be determined by titration against a known amount of oxalic acid, H2C204, according to the following equation ... 

Assay Transfer about 1.2 g of sample, accurately weighed, into a 100-mL volumetric flask, dissolve in and dilute to volume with water, and mix. Pipet 10 mL of this solution into a mixture of 50.0 mL of 0.1 A potassium permanganate, 100 mL of water, and 5 mL of sulfuric acid, keeping the tip of the pipet well below the surface of the liquid. Warm the solution to 40°, allow it to stand for 5 min, and add 25.0 mL of 0.1 A oxalic acid. Heat the mixture to about 80°, and titrate with 0.1 A potassium permanganate. Each milliliter of 0.1 A potassium permanganate is equivalent to 4.255 mg of KN02. Lead Determine as directed under Lead Limit Test, Appendix IIIB, using 1 g of sample in 10 mL of water, and 4 xg of lead (Pb) ion in the control. 

A potassium permanganate solution is standardized by dissolving 0.9234 g sodium oxalate in dilute sulfuric acid and then titrating with the potassium permanganate solution. The principal products of the reaction are man-ganese(II) ion and carbon dioxide gas. The titration requires 18.55 mL of the potassium permanganate solution to reach the endpoint, which is indicated by the first permanent, but barely perceptible, pink color of the permanganate ion. 

Unfortunately, potassium permanganate is not obtainable in high enough purity and can undergo decomposition by exposure to sunlight. Therefore it cannot be used as a primary standard (p. 143). However, it can be used in redox titrations provided it is standardized with sodium oxalate (which is available in high purity). The redox reaction involving oxalate is as follows ... 

An accurately weighed portion of sodium oxalate (0.1550g) was dissolved in dilute sulphuric acid (250 mL). Whilst maintaining the temperature of the solution above 70 °C, it was titrated to equivalence with potassium permanganate solution (18.5 mL). What is the molarity of potassium permanganate ... 

These direct titrations form the basis of more complicated analytical procedures. Many analytical procedures are indirect and involve additional preliminary reactions of the sample before the titration can be carried out. For example, a soluble calcium salt will not take part in a redox reaction with potassium permanganate. But adding ammonium oxalate to the solution containing Ca causes the quantitative precipitation of calcium oxalate ... 

For example, we showed in earlier chapters that the calcium ion concentration of an aqueous solution is readily determined by titration with a standard EDTA solution or by potential measurements with a specific-ion electrode. Alternatively, the calcium content of a solution can be determined either from atomic absorption or atomic emission measurements or by the precipitation of calcium oxalate followed by weighing or titrating with a standard solution of potassium permanganate. 

One-milliliter samples of the suspension are pipetted into measured excess volumes of standard oxalic acid solution. Each sample is diluted to 100 ml., and the unoxidized oxalic acid is then titrated with 0.1 N potassium permanganate solution which has been standardized against oxalic acid. Since the concentration of crystals in the anolyte is not absolutely uniform, the material yield calculated from the quantity of oxidizing agent present depends upon the region from which the sample is taken. Larger samples are analyzed electrometrically because of the indefiniteness of the visual end point.1... 

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